Method of Obtaining or Maintaining Optical Transmittance into Boiler Liquid

ABSTRACT

A clean-in-place method of maintaining optical transference through a light transference medium operably connected to a boiler system is disclosed. The method comprises inter alia contacting a liquid chemical agent to a wetted surface of a light transference medium. The liquid chemical agent is selected from the group consisting of an acid, a chelant, a reducing agent, and combinations thereof, for a period of time and at a concentration sufficient to clean the wetted surface of the light transference medium.

BACKGROUND

Measurement of parameters in liquids using optical sensors is commonplace. Reliable measurement of such parameters generally requires light to pass into the liquid, which generally requires light to first pass through a reasonably transparent medium, e.g., a light transference medium. Reliability issues can arise in the event of obstruction of optical transference through the medium, which may be caused by particulate matter.

Generally, boiler liquids are deaerated liquids that have unique features. Some unique features of boiler liquids include having very low levels of dissolved oxygen (e.g., less than about 10 ppb dissolved oxygen in conventional boiler feedwater) and having a pH of from about 9 to about 11. Particularly in boiler systems utilizing a form of treatment control based on light detection and/or measurement (e.g., fluorometry), some amount of corrosion will occur over time and deposit in the form of particulate matter onto a light transference medium, thereby causing some amount of optical obstruction of the light transference medium. Regarding detection and measurement methods that utilize light transference, the unique conditions of deaerated liquids, particularly boiler liquid, present a challenge to the user when a light transference medium becomes optically obstructed. Ideally, optical obstruction can be altogether prevented, and if optical obstruction occurs, it can be removed without disrupting detection, measurement, and/or treatment control via the light transference.

SUMMARY

A clean-in-place method of maintaining optical transference through a light transference medium operably connected to a boiler system is provided. The clean-in-place method comprises contacting a stream of boiler water with a wetted surface of a light transference medium in optical communication with an optical sensor. Data related to a parameter of the boiler liquid measured by the optical sensor is input to a control scheme of a boiler system. The optical sensor is electronically isolated from the control scheme, which maintains control of the boiler system based on the input data related to the parameter of the boiler liquid. A liquid chemical agent contacts the wetted surface of the light transference medium for a period of time and at a concentration sufficient to clean the wetted surface of the light transference medium. The liquid chemical agent is selected from the group consisting of: an acid, a chelant, a reducing agent, and combinations thereof. The liquid chemical agent is removed from the wetted surface of the light transference medium, and the optical sensor is electronically de-isolated from the control scheme.

Additionally, a clean-in-place method of maintaining optical transference through a light transference medium operably connected to a boiler system is provided. The clean-in-place method comprises flowing a stream of boiler liquid to contact a wetted surface of a light transference medium in optical communication with an optical sensor. Data related to a parameter of the boiler liquid measured by the optical sensor is input to a control scheme of a boiler system. The flow of the stream of boiler liquid to contact the wetted surface of the light transference medium is discontinued. The optical sensor is electronically isolated from the control scheme, which maintains control of the boiler system based on the input data related to the parameter of the boiler liquid. A liquid chemical agent contacts the wetted surface of the light transference medium for a period of time and at a concentration sufficient to clean the wetted surface of the light transference medium. The liquid chemical agent is selected from the group consisting of: an acid, a chelant, a reducing agent, and combinations thereof. The liquid chemical agent is removed from the wetted surface of the light transference medium, the flow of the stream of boiler liquid to contact the wetted surface of the light transference medium is resumed, and the optical sensor is electronically de-isolated from the control scheme.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 illustrates an embodiment of a system that may be used to carry out the methods disclosed herein;

FIG. 2 is a plot of results of Example 1 related to treatment using urea hydrochloride;

FIG. 3 is a plot of results of Example 2 related to treatment using oxalic acid;

FIG. 4 is a plot of results of Example 3 related to treatment using sodium hydrosulfite;

DETAILED DESCRIPTION

While embodiments encompassing the general inventive concepts may take various forms, there is shown in the drawings and will hereinafter be described various illustrative and preferred embodiments with the understanding that the present disclosure is to be considered an exemplification and is not intended to be limited to the specific embodiments.

Methods of maintaining optical transference through a light transference medium and into boiler liquid, which is generally a deaerated liquid, are provided. The methods include contacting a liquid chemical agent to a wetted surface of the light transference medium for a period of time and at a concentration sufficient to clean the wetted surface of the light transference medium. The boiler liquid is generally boiler blowdown liquid.

As it pertains to this disclosure, unless otherwise indicated, “controller” refers to an electronic device having components such as a processor, memory device, digital storage medium, cathode ray tube, liquid crystal display, plasma display, touch screen, or other monitor, and/or other components. Controllers include, for example, an interactive interface that guides a user, provides prompts to the user, or provides information to the user regarding any portion of the method of the invention. Such information may include, for example, building of calibration models, data collection of one or more parameters, measurement location(s), management of resulting data sets, etc.

The controller is preferably operable for integration and/or communication with one or more application-specific integrated circuits, programs, computer-executable instructions or algorithms, one or more hard-wired devices, wireless devices, and/or one or more mechanical devices such as liquid handlers, hydraulic arms, servos, or other devices. Moreover, the controller is operable to integrate feedback, feed-forward, or predictive loop(s) resulting from, inter alia, the parameters measured by practicing the method(s) of the present disclosure. Some or all of the controller system functions may be at a central location, such as a network server, for communication over a local area network, wide area network, wireless network, extranet, the Internet, microwave link, infrared link, and the like, and any combinations of such links or other suitable links In addition, other components such as a signal conditioner or system monitor may be included to facilitate signal transmission and signal-processing algorithms.

By way of example, the controller is operable to implement the method of the invention in a semi-automated or fully-automated fashion. In another embodiment, the controller is operable to implement the method in a manual or semi-manual fashion.

Data transmission of any of the measured parameters or signals to a user, chemical pumps, alarms, or other system components is accomplished using any suitable device, such as a wired or wireless network, cable, digital subscriber line, internet, etc. Any suitable interface standard(s), such as an ethernet interface, wireless interface (e.g., IEEE 802.11a/b/g/n, 802.16, Bluetooth, optical, infrared, other radiofrequency, any other suitable wireless data transmission method, and any combinations of the foregoing), universal serial bus, telephone network, the like, and combinations of such interfaces/connections may be used. As used herein, the term “network” encompasses all of these data transmission methods. Any of the components, devices, sensors, etc., herein described may be connected to one another and/or the controller using the above-described or other suitable interface or connection. In an embodiment, information (collectively referring to all of the inputs or outputs generated by the method of the invention) is received from the system and archived. In another embodiment, such information is processed according to a timetable or schedule. In a further embodiment, such information is processed in real-time. Such real-time reception may also include, for example, “streaming data” over a computer network.

As it pertains to this disclosure, unless otherwise indicated, “control scheme” refers to providing output based on input from a controller as defined herein.

A clean-in-place method of maintaining optical transference through a light transference medium operably connected to a boiler system is provided. The clean-in-place method comprises contacting a stream of boiler water with a wetted surface of a light transference medium in optical communication with an optical sensor. Data related to a parameter of the boiler liquid measured by the optical sensor is input to a control scheme of a boiler system. The optical sensor is electronically isolated from the control scheme, which maintains control of the boiler system based on the input data related to the parameter of the boiler liquid. A liquid chemical agent contacts the wetted surface of the light transference medium for a period of time and at a concentration sufficient to clean the wetted surface of the light transference medium. The liquid chemical agent is selected from the group consisting of: an acid, a chelant, a reducing agent, and combinations thereof. The liquid chemical agent is removed from the wetted surface of the light transference medium, and the optical sensor is electronically de-isolated from the control scheme.

A clean-in-place method of maintaining optical transference through a light transference medium operably connected to a boiler system is also provided. The clean-in-place method comprises flowing a stream of boiler liquid to contact a wetted surface of a light transference medium in optical communication with an optical sensor. Data related to a parameter of the boiler liquid measured by the optical sensor is input to a control scheme of a boiler system. The flow of the stream of boiler liquid to contact the wetted surface of the light transference medium is discontinued. The optical sensor is electronically isolated from the control scheme, which maintains control of the boiler system based on the input data related to the parameter of the boiler liquid. A liquid chemical agent contacts the wetted surface of the light transference medium for a period of time and at a concentration sufficient to clean the wetted surface of the light transference medium. The liquid chemical agent is selected from the group consisting of: an acid, a chelant, a reducing agent, and combinations thereof. The liquid chemical agent is removed from the wetted surface of the light transference medium, the flow of the stream of boiler liquid to contact the wetted surface of the light transference medium is resumed, and the optical sensor is electronically de-isolated from the control scheme.

The terms “optical” and “light” are used interchangeably herein. Utilization of the phrase “into boiler liquid” is intended to cover light transmission in any direction between the boiler liquid, the light transference medium, a light source, and/or a light detector. For example, the optical signal may originate from within the boiler liquid and be transferred to a sensor via the light transference medium (e.g., fluorometric emission), or from a light source through the light transference medium and into the boiler liquid (e.g., fluorometric excitation). Illustrative embodiments of optical sensors that perform optical measurements using optical signals include, but are not limited to, devices capable of detecting or sensing absorbance, colorimetric, refractometric, spectrophotometric, luminometric, and/or fluorometric signals, or images. In a preferred embodiment, the optical signal comprises a fluorometric excitation and/or emission.

The method is directed to obtaining or maintaining optical transference into boiler liquid in contact with a light transference medium. The method can be utilized to remove obstructions that may be present on the light transference medium. Removal of obstruction from the light transference medium sufficient to allow for optical transference, thereby allowing for performance of an optical measurement of the boiler liquid, is also achieved by the methods of the present invention.

The term “clean-in-place” is utilized herein to describe a method that is performed without disassembly of the system. For example, the light transference medium is not removed from the system, and the system is not disconnected to gain physical access to the light transference medium (e.g., to be manually wiped), to carry out a clean-in-place method. Related to the methods described herein, the light transference medium remains operably connected to a boiler system, though the stream of boiler liquid may be diverted so as to not contact the wetted surface of the light transference medium during performance of the disclosed methods.

When performing the methods described herein, the optical transference through the light transference medium may be at least partially obstructed by particulate matter. The particulate matter may comprise particulate matter typically found in raw water, e.g., mud, sand, silt, etc. The particulate matter may comprise a metal oxide. The oxide may be of a metal selected from the group consisting of iron, copper, manganese, titanium, chromium, nickel and combinations thereof. Metal oxide deposition is of particular concern for boiler liquid, particularly boiler blowdown liquid. In certain embodiments, the particulate matter comprises at least one of silica, a calcium oxide, a calcium salt, a magnesium oxide, and a magnesium salt.

The timing of the contacting of the liquid chemical agent to the wetted surface of the light transference medium may take any one or more of several forms. In certain embodiments, the liquid chemical agent is added continuously to the boiler liquid, which preferably includes during operation of the system utilizing the liquid chemical agent. In other embodiments, the liquid chemical agent is added intermittently to the boiler liquid, e.g., for a timed duration at timed intervals. In further embodiments, the liquid chemical agent is added on an as-needed basis, which can be determined, e.g., by comparing historical data related to the relevant sensor and light transference medium. For embodiments where the flow of the stream the boiler liquid is discontinued, the liquid chemical agent may be contacted intermittently or on an as-needed basis.

In embodiments of the present invention, the light transference medium is in optical communication with an optical sensor, which allows the optical sensor to be utilized to monitor a substance using optical detection methods. For example, a flow cell is generally used to allow for fluorometric detection of a component of a liquid flowing through a conduit. The flow cell allows for light to pass between a fluorometer and the flowing liquid via the wall of the flow cell, thereby allowing the fluorometer to carry out its monitoring without physically contacting the flowing liquid. For the given situation, the fluorometer is said to be in optical communication with the flow cell.

Examples of light transference media include, but are not limited to, a flow cell, an optical window, a reflective surface, a refractive surface, a dispersive element, a filtering element, and an optical fiber sensor head. The light transference medium may be constructed of a material that is transparent or nearly transparent. The light transference medium may have a hardness of at least about 7 on the Mohs scale. The term “transparent or nearly transparent” refers to the ability of light to pass through a substance sufficient to use light for detection and/or measurement purposes as discussed herein, which includes transparency as defined by ASTM D1746. The hardness of the light transference medium becomes increasingly important when ultrasonic energy is utilized to supplement the general clean-in-place methods disclosed herein. In certain embodiments, the light transference medium is constructed of quartz, sapphire, or diamond.

In certain embodiments, the light transference medium is constructed of any suitable transparent or nearly transparent composition, and is coated with a transparent or nearly transparent substance having a hardness of at least about 7 on the Mohs scale. For example, the light transference medium may be constructed of a substance having a Mohs scale hardness of at least about 7 (e.g., quartz), and then coated with a substance having an even higher Mohs scale rating. In certain embodiments, the coating substance has a Mohs scale rating of from about 8 to 10, or from about 9 to 10, or 10. Illustrative embodiments of substances suitable for coating a light transference medium include, but are not limited to, diamond, titanium diboride, boron nitride, and sapphire.

In certain embodiments, the light transference medium takes the form of a reflective surface. In embodiments utilizing a reflective surface, an optical window may be utilized in concert with the reflective surface to provide observation from outside the boiler liquid.

In certain embodiments, treatment of the boiler liquid is controlled by utilizing the measured parameter in a control scheme. Treatment of the boiler liquid may include, but is not limited to, at least one of physical treatment and chemical treatment. Non-limiting examples of physical treatment include adjustment of any of the following parameters of the boiler liquid: temperature, pressure, physical phase, flow rate (e.g., circulation, blowdown, and/or make-up), flow path, and mixing. Non-limiting examples of chemical treatment include adjustment of any of the following parameters, all related to a treatment chemical: chemical species selection, chemical species concentration, chemical species dosage rate, chemical species dosage location, and deaeration completeness.

In the methods disclosed herein, the measured parameter is inputted into a control scheme. The control scheme is generally an automated method that inputs a plurality of several measured parameters and operates several process devices, e.g., pumps, valves, etc. For example, a certain measured parameter may indicate that treatment chemical concentration has fallen outside a lower tolerance limit. For the present example, the measured parameter may trigger the control scheme to operate a feed pump, which in turn adds treatment chemical to the process.

In certain embodiments, the optical sensor is electronically isolated from the control scheme. A sensor is said to be electronically isolated if it generates data that is intentionally ignored or otherwise intentionally not acted upon by a controller, or provides no data because of an action of the controller (e.g., automatically shut down) or the user (e.g., unplugged). A sensor that is electronically isolated in the exemplary manner may allow for the sensor to be cleaned, e.g., via liquid chemical treatment, without providing false or misleading data acquired during said liquid chemical treatment. An electronically isolated sensor would not need to be physically isolated from the stream of boiler liquid, but isolated only from the control scheme. The term “meaningful data” as used herein refers to data that describes a parameter of a substance and may be input into and reliably acted upon by a control scheme.

In certain embodiments, flow of the stream of boiler liquid in contact with the wetted surface of the light transference medium is discontinued in order to carry out the contacting the liquid chemical agent step. A light transference medium can be said to undergo “system isolation” when the flow of the stream of boiler liquid is discontinued to carry out a clean-in-place method such as, e.g., those disclosed herein. System isolation allows for the liquid chemical agent to contact the wetted surface of the light transference medium for an extended period of time, as opposed to dosing the liquid chemical treatment into the flowing stream of boiler liquid.

After the liquid chemical agent has contacted the wetted surface for a period of time and at a concentration sufficient to clean the wetted surface, the liquid chemical agent is removed from the wetted surface and flow of the stream of boiler liquid is resumed. In certain embodiments, the liquid chemical agent is removed by resuming the flow of the stream of boiler liquid to contact the wetted surface of the light transference medium.

In embodiments that carry out system isolation, the liquid chemical agent may be brought into contact with the wetted surface and remain static for a period of time. In a further embodiment, after the liquid chemical agent has been removed from the wetted surface, a further liquid chemical agent, whether it be the same species of liquid chemical agent or a different species of liquid chemical agent, may be brought into contact with the wetted surface and remain static for a period of time, prior to resuming the flow of the stream of boiler liquid to contact the wetted surface of the light transference medium. In other embodiments that carry out system isolation, the liquid chemical agent may contact the wetted surface by being passed across the wetted surface for a period of time, e.g., in a liquid chemical treatment loop, or the liquid chemical agent may be pass across the wetted surface only once.

In embodiments of the inventive methods, cleaning via liquid chemical agent contact requires that the liquid chemical agent contacts the wetted surface for a period of time and at a concentration sufficient to clean the wetted surface of the light transference medium. The period of time and the concentration generally depend on each other, with a shorter period of contact time generally necessary to achieve cleaning using higher liquid chemical agent concentrations, and a longer period of contact time for lower liquid chemical agent concentration, assuming that all other factors remain constant (temperature, species of liquid chemical agent, materials of construction, etc.). A period of time sufficient to clean the wetted surface may be nearly instantaneous, e.g., 1 second or less, for a given liquid chemical agent dosed to a slightly-obstructed light transference medium at a reasonably high concentration and otherwise under preferential conditions. Cleaning a heavily-obstructed light transference medium may require a significantly longer contact time, e.g., 20 minutes or greater, depending on inter alia liquid chemical agent selection and concentration. In a preferred embodiment, the period of time is from about 30 seconds to about 20 minutes, including from about 1 minute to about 10 minutes.

The liquid chemical agent should be selected and dosed so as to provide cleaning of the wetted surface without corroding or otherwise damaging the surfaces contacted by the liquid chemical agent. With few exceptions, a higher concentration of liquid chemical agent will generally provide better cleaning activity when contacting the wetted surface. One notable exception is sulfuric acid, which may perform better when fully-protonated. In embodiments that utilize sulfuric acid, the sulfuric acid may have a concentration of from about 5 weight percent to about 98 weight percent in aqueous solution. In a preferred embodiment that utilizes sulfuric acid, the sulfuric acid has a concentration of from about 5 weight percent to about 15 weight percent, including about 10 weight percent, in aqueous solution. In embodiments that utilize citric acid, the citric acid may have a concentration of from about 5 weight percent to about 30 weight percent in aqueous solution. In a preferred embodiment that utilizes citric acid, the citric acid has a concentration of from about 5 weight percent to about 15 weight percent, including about 10 weight percent, in aqueous solution.

In embodiments that do not carry out system isolation of the light transference medium subject to the clean-in-place methods disclosed herein, the liquid chemical agent may contact the wetted surface of the light transference medium at a flow rate of about 1 mL/min to about 40 mL/min at a concentration of about 0.1 weight percent to about 80 weight percent, depending on, inter alia, the liquid chemical agent utilized. In a preferred embodiment, the liquid chemical agent contacts the wetted surface of the light transference medium at a flow rate of about 1 mL/min to about 40 mL/min at a concentration of about 1 weight percent to about 20 weight percent chelant in aqueous solution. In another preferred embodiment, the liquid chemical agent contacts the wetted surface of the light transference medium at a flow rate of about 1 mL/min to about 40 mL/min at a concentration of about 0.1 weight percent to about 10 weight percent reducing agent in aqueous solution. In yet another preferred embodiment, the liquid chemical agent contacts the wetted surface of the light transference medium at a flow rate of about 1 mL/min to about 40 mL/min at a concentration of about 30 weight percent to about 60 weight percent acid in aqueous solution. Each preferred embodiment is further described herein in the context of components of the liquid chemical agent.

In certain embodiments that undergo electronic isolation or system isolation of a light transference medium and/or optical sensor, control of the boiler system may be maintained based on data input into the control scheme prior to the electronic or system isolation. Control of the boiler system may be maintained based on data gathered from a period of time previous to the electronic or system isolation. The period of time previous to the electronic or system isolation may be, e.g., the last recorded value(s) prior to the electronic or system isolation, or e.g., one minute, or five minutes, or one hour, or five hours, etc. The gathered data may be manipulated as is known in the art to implement the maintenance of boiler system control. Averaging data over a period of time is an example of manipulating data.

As mentioned in the previous paragraph, the boiler system may be maintained based on the last recorded value prior to the electronic or system isolation. By way of example, the optical sensor may input a data point related to a parameter of the boiler liquid, and the optical sensor and its corresponding light transference medium may be electronically or systemically isolated immediately following the input of the data point. In this preferred embodiment of the invention, the control scheme continues to maintain control of the boiler system as if the optical sensor continues to input the same data that was input immediately prior to the electronic or system isolation. Instead of utilizing the immediate predecessor data point to maintain control, further exemplary embodiments may utilize, for example, several prior data points, a mean of several data points, a median of several data points, a mode of several data points, or a statistical trend of several data points.

In embodiments of the inventive methods, the liquid chemical agent comprises a component selected from the group consisting of an acid, a chelant, a reducing agent, and combinations thereof. Single component liquid chemical agents can be used to successfully clean a light transference medium according to the inventive methods disclosed herein. However, in a particularly preferred embodiment, the liquid chemical agent comprises an acid of one chemical species and a chelant of a second chemical species. In another particularly preferred embodiment, the liquid chemical agent comprises a reducing agent of one chemical species and a chelant of a second chemical species. The phrase “of one chemical species . . . of a second chemical species” is used to describe the utilization of distinct chemicals for each named genus. For example, a liquid chemical agent comprising a reducing agent of one chemical species and a chelant of a second chemical species may be a liquid chemical agent comprising sodium hyposulfite (a reducing agent of one chemical species) and oxalic acid (a chelant of a second chemical species). An exemplary embodiment of a liquid chemical agent comprising an acid of one chemical species and a chelant of a second chemical species is a liquid chemical species comprising urea hydrochloride (an acid of one chemical species) and oxalic acid (a chelant of a second chemical species).

In certain embodiments, the component of the liquid chemical agent is an acid selected from the group consisting of: urea hydrochloride, hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, acetic acid, citric acid, carbonic acid, bicarbonic acid, sulfamic acid, and combinations thereof. In a preferred embodiment, the acid in the liquid chemical agent is urea hydrochloride.

When selected, the acid may be present in the liquid chemical agent at a concentration of from about 5 weight percent to about 98 weight percent in aqueous solution, including from about 20 weight percent to about 80 weight percent acid in aqueous solution, and further including at least about 20 weight percent, or at least about 30 weight percent, or about 40 weight percent to about 50 weight percent, to about 60 weight percent, to about 70 weight percent, to about 80 weight percent acid in aqueous solution. In a preferred embodiment, the acid is present in the liquid chemical agent at a concentration of about 30 weight percent to about 60 weight percent.

In certain embodiments, the component of the liquid chemical agent is a chelant selected from the group consisting of: citric acid, oxalic acid, ethylenediaminetetraacetic acid, diethylene triamine pentaacetic acid, an organic phosphonate, salts thereof, and combinations thereof. In a preferred embodiment, the chelant in the liquid chemical agent is oxalic acid.

When selected, the chelant may be present in the liquid chemical agent at a concentration of from about 0.1 weight percent to about 20 weight percent chelant in aqueous solution, including at least about 0.1 weight percent, or at least about 0.5 weight percent or at least about 1 weight percent, to about 3 weight percent, or about 5 weight percent, or about 10 weight percent, or about 20 weight percent chelant in aqueous solution. In a preferred embodiment, the chelant is present in the liquid chemical agent at a concentration of from about 1 weight percent to about 3 weight percent chelant in aqueous solution.

In certain embodiments, the component of the liquid chemical agent is a reducing agent selected from the group consisting of: an acid sulfite, an acid bisulfite, an acid hydrosulfite, an acid phosphite, phosphoric acid, oxalic acid, formic acid, ascorbic acid, erythorbic acid, salts thereof, and combinations thereof. In a preferred embodiment, the reducing agent in the liquid chemical agent is sodium hydrosulfite.

When selected, the reducing agent may be present in the liquid chemical agent at a concentration of from about 0.1 weight percent to about 10 weight percent reducing agent in aqueous solution, including from about 0.1 weight percent, or about 0.3 weight percent, or about 0.5 weight percent, to about 3 weight percent, or to about 7 weight percent, or to about 10 weight percent reducing agent in aqueous solution. In a preferred embodiment, the reducing agent is present in the liquid chemical agent at a concentration of from about 0.5 weight percent to about 3 weight percent reducing agent in aqueous solution.

Of note, a particular chemical species may overlap into any two, and in some instances, all three, of the three chemical genuses of the present invention. For example, citric acid and oxalic acid can be considered both an acid and a chelant. Furthermore, several acids, including oxalic acid and phosphoric acid, can be considered to be reducing agents in addition to acids and/or chelants.

Referring to FIG. 1, operation of a boiler treatment system generally involves boiler liquid 10 flows through solenoid valve 12 a and continues through light transference medium (e.g., flow cell) 20, contacting wetted surface 21, and usually out to auxillary operations via valve 12 b or to treatment or a drain via valve 12 c. A parameter of boiler liquid 10 is measured using optical sensor 22 (e.g., fluorometer), which is in operable communication with light transference medium 20, and data related to the parameter is input into a control scheme (e.g., relayed to controller 100). Optical sensor 22 is electronically isolated from the control scheme, which maintains control of the boiler system based upon the previously input data. A liquid chemical agent, e.g., present in container 50, is brought into contact with wetted surface 21 via pump 54, flowing through valve 52 and check valve 56 and on to wetted surface 21. Optionally, boiler liquid 10 can be diverted to bypass line 70 by closing valve 12 a and opening valve 12 d. As is readily recognized by one skilled in the art, valves 12 a and 12 d can be replaced by a single three-way valve (not shown), which could be operably configured to divert boiler liquid 10 from wetted surface 21 of light transference medium 20 and to bypass line 70. Optionally, valves 12 a, 12 b, 12 c, and 12 d can be operably actuated to provide system isolation of light transference medium 20. The liquid chemical agent may continuously or intermittently contact wetted surface 21, or may be periodically contacted and removed from wetted surface via system isolation as described herein.

To supplement the more general clean-in-place methods disclosed herein, ultrasonic energy may be applied into the liquid chemical agent during at least a portion of the contacting of the liquid chemical agent to the wetted surface of the light transference medium. When utilized, the ultrasonic energy further effectuates cleaning of the wetted surface of the light transference medium. The ultrasonic energy may be applied via an ultrasonic probe and ultrasonic transducer in a manner disclosed in U.S. Patent Application Publication No. 2013/0186188, filed Jan. 19, 2012, to Bradley et al., or in a manner disclosed in U.S. patent application Ser. No. 14/592,219, filed Jan. 8, 2015, to Hicks et al., each disclosure of which is incorporated herein by reference in its entirety. The embodiment illustrated in FIG. 1 includes optional ultrasonic probe 201 operably attached to optional ultrasonic transducer 202.

The following examples further illustrate the invention but, of course, should not be construed as in any way limiting its scope.

EXAMPLE 1

Three cleaning chemicals have been tested to be able to remove iron oxide particles from boiler water stream.

Urea hydrochloride, available as DC-14 from Nalco Company, 1601 West Diehl Road, Naperville, Ill. 60563, was tested as a liquid cleaning agent to clean a wetted surface of a flow cell used to monitor a boiler blowdown stream of a power house boiler. A control flow cell was continuously exposed to the same boiler blowdown stream and was not cleaned. The duration of the test was approximately 28 days. The urea hydrochloride had a concentration of 30-60% by weight in aqueous solution, having a pH of 1.5. Aqueous urea hydrochloride at this concentration generally vaporizes at normal operational conditions. The urea hydrochloride was dosed once per day at full concentration, i.e., not further diluted, and allowed to contact the wetted surface of the test flow cell for 3 minutes under system isolation.

FIG. 2 illustrates the results of testing. The spikes in cell obstruction represent the periods of time during which the urea hydrochloride was dosed to the wetted surface of the flow cell. Notice the measured increase in cell obstruction of the control flow cell versus the significantly lower cell obstruction of the test flow cell during non-treatment time periods. For example, at Day 15, the control flow cell is nearly 40% obstructed while the test flow cell is less than 10% obstructed, which is believed to be unobstructed. While not wishing to be bound by theory, any amount of measured obstruction that is less than 10% is believed to be caused by light absorbance of water or LED decay of the optical sensor.

EXAMPLE 2

Oxalic acid was tested as a liquid cleaning agent to clean a wetted surface of a flow cell used to monitor a boiler blowdown stream of a power house boiler. A control flow cell was continuously exposed to the same boiler blowdown stream and was not cleaned. The duration of the test was approximately 25 days. The oxalic acid had a concentration of 12,000 ppm by weight in aqueous solution, having a pH of 2, which was stable at 50° C. A higher pH would be expected at a lower concentration. The oxalic acid was dosed at full concentration, i.e., not further diluted, and allowed to contact the wetted surface of the test flow cell for 10 minutes under system isolation. FIG. 3 illustrates the results of testing, with the spikes in cell obstruction represent the periods of time during which the oxalic acid was dosed to the wetted surface of the flow cell. Notice the measured increase in cell obstruction of the control flow cell versus the significantly lower cell obstruction of the test flow cell during non-treatment time periods. For example, at Day 11, the control flow cell is approximately 10% obstructed while the test flow cell is almost completely unobstructed. Furthermore, when oxalic acid is not dosed to the test flow cell (e.g., Days 16-20), obstruction of the test flow cell generally tracks the obstruction of the control flow cell. However, obstruction of the test flow cell decreases dramatically after oxalic acid contacts the test flow cell's wetted surface.

EXAMPLE 3

Sodium hydrosulfite was tested as a liquid cleaning agent to clean a wetted surface of a flow cell used to monitor a boiler blowdown stream of a power house boiler. A control flow cell was continuously exposed to the same boiler blowdown stream and was not cleaned. The duration of the test was approximately 38 days. The sodium hydrosulfite had a concentration of 0.8-2.4 weight percent in aqueous solution, which decomposes to sulfur dioxide at above 50° C. The sodium hydrosulfite was dosed at full concentration, i.e., not further diluted, and allowed to contact the wetted surface of the test flow cell for 10 minutes under system isolation.

FIG. 4 illustrates the results of testing. The spikes in cell obstruction represent the periods of time during which the sodium hydrosulfite was dosed to the wetted surface of the test flow cell under system isolation. Notice the measured increase in cell obstruction of the control flow cell versus the significantly lower cell obstruction of the test flow cell, particularly beginning at approximately Day 28.

EXAMPLE 4

Experiments were performed to test certain combinations of components of the liquid cleaning agents of Examples 1-3. The following aqueous agents were obtained or prepared: sodium hydrosulfite at 0.8-2.4% by weight; oxalic acid at 1.2% by weight (as dihydrate); and urea hydrochloride as 30-60% by weight. The following combinations were created from the aqueous agents, each blended at 1:1 volume ratios:

Combination No. Agents 1 Sodium hydrosulfite + oxalic acid 2 Urea hydrochloride + oxalic acid 3 Urea hydrochloride + sodium hydrosulfite

Flow cells of various obstructions (60-100%) were placed in each of the combined liquid cleaning agents for 10 minutes at a time, removed, and observed to determine each combination's performance. Combinations 2 and 3 removed some of the obstructing deposition, and Combination 1 removed substantially all of the obstructing deposition.

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

The use of the terms “a” and “an” and “the” and “at least one” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term “at least one” followed by a list of one or more items (for example, “at least one of A and B”) is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. 

1-14. (canceled)
 15. A clean-in-place method of maintaining optical transference through a light transference medium operably connected to a boiler system, the method comprising: contacting a stream of boiler liquid with a wetted surface of a light transference medium in optical communication with an optical sensor; inputting data related to a parameter of the boiler liquid measured by the optical sensor to a control scheme of a boiler system; electronically isolating the optical sensor from the control scheme while maintaining control of the boiler system based on the input data related to the parameter of the boiler liquid; contacting a liquid chemical agent to the wetted surface of the light transference medium, the liquid chemical agent comprising a component selected from the group consisting of an acid, a chelant, a reducing agent, and combinations thereof, for a period of time and at a concentration sufficient to clean the wetted surface of the light transference medium; and electronically de-isolating the optical sensor from the control scheme.
 16. The clean-in-place method of claim 15, wherein the component is an acid selected from the group consisting of: urea hydrochloride, hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, acetic acid, citric acid, carbonic acid, bicarbonic acid, sulfamic acid, and combinations thereof.
 17. The clean-in-place method of claim 16, wherein the acid is present in the liquid chemical agent at a concentration of from about 5 weight percent to about 98 weight percent acid in aqueous solution.
 18. The clean-in-place method of claim 15, wherein the component is a chelant selected from the group consisting of: citric acid, oxalic acid, ethylenediaminetetraacetic acid, diethylene triamine pentaacetic acid, an organic phosphonate, salts thereof, and combinations thereof.
 19. The clean-in-place method of claim 18, wherein the chelant is present in the liquid chemical agent at a concentration of from about 1 weight percent to about 20 weight percent chelant in aqueous solution.
 20. The clean-in-place method of claim 15, wherein the component is a reducing agent selected from the group consisting of: an acid sulfite, an acid bisulfate, an acid hydrosulfite, an acid phosphite, phosphoric acid, oxalic acid, formic acid, ascorbic acid, erythorbic acid, salts thereof, and combinations thereof.
 21. The clean-in-place method of claim 20, wherein the reducing agent is present in the liquid chemical agent at a concentration of from about 0.1 weight percent to about 10 weight percent reducing agent in aqueous solution.
 22. The clean-in-place method of claim 15, wherein the liquid chemical agent comprises an acid of one chemical species and a chelant of a second chemical species.
 23. The clean-in-place method of claim 15, wherein the liquid chemical agent comprises a reducing agent of one chemical species and a chelant of a second chemical species.
 24. The clean-in-place method of claim 15, further comprising applying ultrasonic energy into the liquid chemical agent during at least a portion of the contacting of the liquid chemical agent to the wetted surface of the light transference medium.
 25. The clean-in-place method of claim 15, wherein the liquid chemical agent contacts the wetted surface of the light transference medium at a flow rate of about 1 L/min to about 40 L/min at a concentration of about 0.1 weight percent to about 80 weight percent.
 26. A clean-in-place method of maintaining optical transference through a light transference medium operably connected to a boiler system, the method comprising: flowing a stream of boiler liquid to contact a wetted surface of a light transference medium in optical communication with an optical sensor; inputting data related to a parameter of the boiler liquid measured by the optical sensor to a control scheme of a boiler system; discontinuing the flow of the stream of boiler liquid to contact the wetted surface of the light transference medium; electronically isolating the optical sensor from the control scheme while maintaining control of the boiler system based on the input data related to the parameter of boiler liquid; contacting a liquid chemical agent to the wetted surface of the light transference medium, the liquid chemical agent comprising a component selected from the group consisting of an acid, a chelant, a reducing agent, and combinations thereof, for a period of time and at a concentration sufficient to clean the wetted surface of the light transference medium; removing the liquid chemical agent from the wetted surface of the light transference medium; resuming the flow of the stream of boiler liquid to contact the wetted surface of the light transference medium; and electronically de-isolating the optical sensor from the control scheme.
 27. The clean-in-place method of claim 26, wherein the component is an acid selected from the group consisting of: urea hydrochloride, hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, acetic acid, citric acid, carbonic acid, bicarbonic acid, sulfamic acid, and combinations thereof.
 28. The clean-in-place method of claim 27, wherein the acid is present in the liquid chemical agent at a concentration of from about 5 weight percent to about 98 weight percent acid in aqueous solution.
 29. The clean-in-place method of claim 25, wherein the component is a chelant selected from the group consisting of: citric acid, oxalic acid, ethylenediaminetetraacetic acid, diethylene triamine pentaacetic acid, an organic phosphonate, salts thereof, and combinations thereof.
 30. The clean-in-place method of claim 29, wherein the chelant is present in the liquid chemical agent at a concentration of from about 1 weight percent to about 20 weight percent chelant in aqueous solution.
 31. The clean-in-place method of claim 26, wherein the component is a reducing agent selected from the group consisting of: an acid sulfite, an acid bisulfate, an acid hydrosulfite, an acid phosphite, phosphoric acid, oxalic acid, formic acid, ascorbic acid, erythorbic acid, salts thereof, and combinations thereof.
 32. The clean-in-place method of claim 31, wherein the reducing agent is present in the liquid chemical agent at a concentration of from about 0.1 weight percent to about 10 weight percent reducing agent in aqueous solution.
 33. The clean-in-place method of claim 26, wherein the period of time is from about 1 minute to about 10 minutes.
 34. The clean-in-place method of claim 26, wherein the liquid chemical agent comprises a reducing agent of one chemical species and a chelant of a second chemical species.
 35. The clean-in-place method of claim 26, further comprising applying ultrasonic energy into the liquid chemical agent during at least a portion of the contacting of the liquid chemical agent to the wetted surface of the light transference medium.
 36. The clean-in-place method of claim 26, wherein the liquid chemical agent is removed by the resuming step. 